| 摘要: | 本論文主要運用次細胞分佈分析法，探討吳郭魚(Oreochromis mossambicus)慢性暴露於不同銅濃度的水體環境中，銅在吳郭魚主要器官之次細胞區塊的累積過程及解毒機制。本研究將吳郭魚暴露於0、0.1、0.3及0.6 ?慊 ml-1的銅濃度下28天進行累積實驗，隨後進行7天的排除實驗，以進行吳郭魚體內器官之次細胞區塊對銅之累積、排除變化量分析。我們以溢出模式(spillover model)來探討各器官對必需元素銅之解毒機制，我們並以一階單區塊累積模式及金屬流入門檻方程式推估各器官之次細胞區塊的吸收速率(uptake rate, ku)、排除速率(elimination rate, ke)、解毒速率(detoxification rate, kd)及生物濃縮因子(bioconcentration factor, BCF)。實驗結果指出，肝臟中銅主要累積在代謝活化區(metabolically active pool, MAP)，並隨著暴露的濃度增加，銅被移往代謝解毒區(metabolically detoxified pool, MDP)進行隔離與解毒；肝並以降低生物動力學的吸收速率(ku)以減少銅累積。而在肌肉及鰓中，銅主要在富含金屬微粒(metal-rich granules, MRG)中進行隔離或儲存，並以加快排除速率(ke)以降低體內的銅累積量。另外，鰓更利用降低吸收速率(ku)來減少銅累積。本研究分析吳郭魚之慢性成長抑制資料與各器官之次細胞區塊累積濃度之相關性來判別活性劑量代表，結果顯示，肝臟之細胞碎片(cell debris)、胞器(organelle)、熱敏感蛋白(heat denature protein)、攝食傳遞區(trophically available fraction, TAF)、代謝活化區(MAP)及代謝解毒區(MDP)皆有顯著關係(r2 =0.8254~0.9211)，其中代謝活化區(MAP)可作為暴露於中、高濃度下成長毒性預估的活性劑量代表。本研究發現吳郭魚在慢性暴露條件下可在各器官之次細胞層次中對銅累積進行調控，了解吳郭魚對銅累積的應對機制，可進一步提升以吳郭魚作為汙染物監測指標的可行性。
In order to understand the metal accumulation and detoxification in tilapia (Oreochromis mossambicus) under various chronic copper (Cu) exposures, we investigated the subcellular distributions of Cu. The tilapia were exposed to 0, 0.1, 0.3, and 0.6 ?慊 ml-1 Cu for 28 days followed by a depuration biosaays of 7 days in water. The relative Cu distribution between the metabolically active pool (MAP) and the metabolically detoxified pool (MDP) were analyzed. The biokinetic parameters, including uptake rate (ku), elimination rate (ke), detoxification rate (kd), and bioconcentration factor (BCF) were obtained. The results revealed that as the concentration of Cu increasing in water, the Cu was transferred from MAP to MDP and the ku of liver was decreased to reduce the toxicify arise from Cu accumulation. Copper was stored mainly at metal-rich granules (MRG) in the gill and muscle. The Cu residue was reduced by increasing ke of gill and muscle, and decreasing ku of gill. The relationship between growth inhibition and Cu residues in organ-specific subcellular fractions were significantly related to cell debris, organelle, heat denature protein (HDP), trophically available fraction (TAF), MAP and MDP in the liver. We found that MAP in the liver can be an indicator for predicting growth toxicity in medium to high exposure concentrations (p<0.05). In conclusion, the subcellular regulation of metal toxicity in tilapia play a key role in mediating the chronic Cu toxicity and provide a basic understanding for field ecological exposure risk assessment. |
